Aluminum clutch Z-bracket replacement

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The Artist formerly known as Turbo84
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I've rounded up most all the material I need to fabricate the new Z-bracket, along with steel material to make a jig for the welding process. I'll be putting short steel sleeves in the ends of the aluminum tube where the assembly rotates on the ball studs. I have two unanswered questions/issues yet:

1) I still have to figure out how much interference fit is needed/appropriate for the steel end sleeves.

2) I need to fabricate a snap ring (inner) groove in the left side sleeve. I haven't come up with a more clever way yet other than using a Dremel tool and a small diameter cutting wheel to cut the groove in the .750" ID steel sleeve. My labor rate is pretty cheap, but I'd still like to minimize the man-hours if I can.

Pictures to follow once I get to a point where there's anything interesting to look at.
 
Well, doing some quick back-of-the-envelope calculations involving the different coefficients of expansion between steel and aluminum, and a guesstimate of the temperature rise of the crosshaft (from storage at ambient temperature to heating up from being downstream of the header pipes), it looks like I won't need an extreme amount of interference fit to deal with the aluminum tubing expanding at a higher rate than the internal steel bushing.

Now I just have to get the correct drill bit size to open up the tube a touch on the left side.
 
How much do you have to open it up? Would an appropriately sized reamer be better to ensure the bore is consistent? We do a lot of press fits for bushings here for similar reasons, and reamers can come in handy to make sure you get the hole just right.
 
How much do you have to open it up? Would an appropriately sized reamer be better to ensure the bore is consistent? We do a lot of press fits for bushings here for similar reasons, and reamers can come in handy to make sure you get the hole just right.

I'm certainly open for suggestions. I don't have any personal experience using a reamer for anything.

The aluminum tube has an ID of .950". I have two bushings that I need to press in. One bushing is 1.010" OD (and about 1.6" long), and the other is 1.060" OD (about an inch long). I need to get the aluminum tubing ID "customized" for each side (still deciding what those ID numbers are), and then hopefully getting the bushings installed/pressed in with the assistance of warming/chilling the different parts.

A second option is to use the same larger OD bushing on both sides. If it simplifies life I could be persuaded to go that way.
 
Let me talk with my Tool & Die shop manager. He's got a lot of experience with this and is the head of the Skunk Works for our engineering experiments at work. I would think that a 1.000" reamed hole might actually be too large for this shrink/press fit application, so maybe 63/64" (0.9844"), but I will check with him to make sure. You certainly don't want it to fall out as the left side header heats up the assembly on longer track days.
 
It looks like if you go with a hole reamed to 63/64", you can then heat up the tube to 450F and drop the bushings in without pressing. The issue with pressing steel into aluminum is that you will sometimes draw up material with it and distort the hole or not get a solid fit. By going shrink fit you should be in better shape. Go ahead and weld the assembly up first, ream the hole to size, put in an oven to preheat the assembly and then drop the bushings in place.

I forget from the other thread, what was the OD on the aluminum tube and what was the ID on the bushing? That can make a slight difference too, but typically a 0.010-0.015" shrink fit is sufficient, so this is more like 0.015-0.025". Once it is all back together, check fit with the ball studs and see if you need to hone the ID of the bushings from any distortion as it shrinks into place. You won't see much heat generated by the pivot action, so that's not the worry, but the ambient heat from being in close proximity to the headers is a different story.
 
just something to consider. Headers tubes surround the bar and are usually around 600 degrees (give or take 100 degrees) during normal running operation. I'm concerned that if you 450 degree heat and slip fit that you'll have expansion problems and even cracking of the aluminum after a few heat cycles (if there's a press fit sleeve inside).
 
just something to consider. Headers tubes surround the bar and are usually around 600 degrees (give or take 100 degrees) during normal running operation. I'm concerned that if you 450 degree heat and slip fit that you'll have expansion problems and even cracking of the aluminum after a few heat cycles (if there's a press fit sleeve inside).

Aluminum has a higher rate of thermal expansion. A steel sleeve inside an aluminum tube will probably get loose, although maybe not enough for it to move. I would still pin the insert if it is long enough for the pin to be beyond the reach of the stud. To your point, if there is a really tight interference fit, the aluminum tube shrinking back on the steel insert during cooling could possibly stress the aluminum enough to eventually crack it. FWIW, I have a couple of aluminum components that have steel (threaded) inserts in them to accept a bolt. The steel inserts appear to be interference fit and knurled to keep them from twisting when torque is applied.

Pappy
 
Back in country.

If you can access a lath the cross-shaft ends can be bored to the exact diameter you've calculated you need for your press fit. You can also grind a bar to make the spring ring groove. If you use the stock plastic seats for the outboard ball stud you might not need a sleeve on that end.

I don't think header heat will be a problem. Lots of air moving down there and the plastic cups for the outer ball stud don't fail. If you don't have access to a pyrometer, take a drive and touch the cross-shaft after.
 
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